diff --git a/api/client-server/room_send.yaml b/api/client-server/room_send.yaml
index 70d005c2..b7ccbcfb 100644
--- a/api/client-server/room_send.yaml
+++ b/api/client-server/room_send.yaml
@@ -48,8 +48,9 @@ paths:
           name: txnId
           type: string
           description: |-
-            The transaction ID for this event. Clients should generate a
-            unique ID; it will be used by the server to ensure idempotency of requests.
+            The transaction ID for this event. Clients should generate an
+            ID unique across requests with the same access token; it will be
+            used by the server to ensure idempotency of requests.
           required: true
           x-example: "35"
         - in: body